The study assessed the levels of some toxic metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) with their potential ecological and human health risks in water, African Catfish (Clarias gariepinus), Tilapia (Oreochromis spilurus niger) and sediment samples from the Lower Usuma dam FCT, Nigeria during two major seasons in a year (rainy and dry seasons). Toxic metal concentrations were determined using Atomic Absorption spectrophotometry (Cd, Cr, Cu, Ni, Pb and Zn) and Atomic Emission Spectrophotometry (for As and Hg), and the results obtained were compared with national and international standards. The ecological and human health risk indices of the toxic metals present in the samples from the Dam were evaluated and interpreted. Tilapia from the dam posed the highest but medium ecological and human health risk due to Pb concentration of up to 7.11 mg/kg; ecological risk index of 35.55 and hazard quotient of 50.78. Overall ecological and human health risks were low due to the low concentrations of other toxic metals determined. As, Cd, Cr, Cu, Hg, Ni and Zn concentrations were all below WHO limits in the LUD water; Ni and Pb were above limits in the African Catfish and Tilapia samples. The data obtained were analyzed using one-way analysis of variance (ANOVA) and significant differences accepted at p ≤ 0.05. There was no statistical difference in the concentrations of toxic metals in water but there was significant difference between the concentrations of toxic metals in the fish and sediment samples. Correlation was found to exist between toxic metals in the water, fish and sediment analyzed from the dam. The ecological and human health risks of toxic metals in Lower Usuma dam require regular checks and monitoring hence, it was recommended by the researcher, that this and similar research work be carried out annually by NESREA and also, as research work by other students of Environmental and Analytical chemistry.
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